G4S admitted that its bungled security contract will cost it in the region of £50 million as it published half-year results today.

The group claimed it had delivered 83 per cent of contracted shifts for the games and that it was confident the Paralympics – which begin tomorrow – would be fully staffed with a security workforce.

Its half-year results revealed a significant drop in pre-tax profits to £61m from £151m the previous year, although profits were held flat on an underlying basis after sales increased 5.8 per cent to £3.9 billion.

G4S’s failure to provide all of the 10,400 contracted guards for London 2012 forced the government to draft in thousands of extra police and soldiers to provide security.

There were also calls for all current and planned government contracts with the firm to be re-examined.

But G4S said it had lost no contracts as a result of the Olympics and insisted it would continue to play a “major role” in the public sector, with a £3.8bn-a-year project pipeline.

The firm’s move into providing services for a number of police forces – as the government unveiled plans to slash officer numbers by 20 per cent – has sparked serious concern from the Police Federation.

The federation’s head of communications Metin Enver told the Star that officers had long-standing concerns about private-sector involvement in policing.

“The Olympics has exacerbated these concerns,” he said.

“At the end of the day we understand that private firms will do what they do, but the problem is that we have a government creating these opportunities.

“G4S is a symptom, the greater illness is that the government are selling off our public services to the highest bidder.”